The Effect Of Cadmium (Cd²⁺) Stress On The Development And Flight Of Spodoptera Exigua And Its Related Physiological Mechanism

Heavy metal pollution has become one of the most important environmental pollution issues.Heavy metals are easily transmitted and enriched Spodoptera exigua,a kind of phytophagous insects with strong migration capability,is a key link in the food chain.However there is no systematic research on the effect of heavy metal stress on the growth and development,the flight ability and the corresponding mechanism.In this paper,the biological parameters such as pupal weight,emergence rate,wing malformation rate,flight performance,related factors such as wing-body radiations and structural parameters,and effects on energy substances in adults,were systematically studied after S.exigua were fed with artificial diet containing five concentrations of Cd²⁺?0,0.2,0.8,3.2,12.8 mg/kg?at the larval stage.The main results are as follows:1 Effects of cadmium stress on biological parameters of S.exiguaAfter pupation,the weight of female and male pupae increased with the increase of cadmium concentration,significant different with the control,but there was no significant difference between the four cadmium treatments.The emergence rate of adults decreased with the increase of cadmium concentration,but,the treatment of 12.8 mg/kg inhibited the emergence rate of adults significantly.The wing malformation rate of adult was significantly decreased in the 0.2 mg/kg and 0.8 mg/kg treatments,while the wing deformity rate of adult was significantly increased under higher concentrations?3.2 mg/kg and 12.8 mg/kg?.The percentage of female adults increased with the increase of cadmium concentration.Cadmium stress prolonged the life span and oviposition period of adults significantly,which made the oviposition increased first and then decreased,while the pre-oviposition duration was not affected.2 Effects of cadmium stress on the flying performance of S.exiguaThere were significant differences in the flight performance of S.exigua adults exposed to different concentrations of cadmium.The 3 day-old female adults stressed by low concentration of cadmium?0.20 mg/kg?were the best fliers with the longest average flight distance?36.96 km?.The flight performance of S.exigua adults exposed to 0.20 mg/kg cadmium was not significantly different from that of the control.With the increase of cadmium concentration,the flight performance of both male and female adults decreased significantly.The negative effects of heavy metal cadmium stress on the performance of male adults were more obvious than those on that of female adults and the proportion of the strong flying individuals in the flying population was significantly different under different concentrations of cadmium.3 Effects of cadmium stress on the wing-body and structural parameters of S.exiguaDifferent concentrations of cadmium increased the body length of S.exigua significantly,and the wing area and wing spread of male moth were increased significantly,wing load reduced and flying muscle ratio increased in 0.2 mg/kg treatment made it more favorable for flight.While the adults of wing loading was not significantly reduce and the flying muscle ratio was significantly lower in 12.8 mg/kg treatment than that of the control,so that its flight performance was significantly lower than that of the control.With the increase of cadmium concentration,the wing roundness of female adults decreased gradually,while that of male adults increased gradually.Cadmium stress had no significant effect on the body shape of female and male adults,indicating that cadmium stress does not affect the aspect ratio of adults.4 Effects of cadmium stress on energy substances of S.exiguaThe effects of cadmium stress at different concentrations on the fresh and dry weight of adults are basically consistent with those of pupal weight.The content of glycogen in female and male adults were increased by cadmium stress,the content of trehalose in male adults were increased,but the content of trehalose in female adults were decreasd,and the accumulation of glycerol ester in female adults were increased,but not affect the content of protein.The content of protein in male adults were decreased by low concentration of cadmium stress,and the different concentration of cadmium stress was not conducive to the accumulation of glycerol ester content in male adults,which was significantly lower than that of the control.Both female and male adults consumed a certain amount of glycogen in the early stage of emergence,and female adults consumed more than the male when under the higher concentration of cadmium stress.The utilization efficiency of glyceride was different and absolute content of glyceride consumed by male adults were significantly higher than that of the female when they flied the same time.